In electric smelting furnaces for the production of ferro alloys, silicon, pig iron etc., it is used consumable carbon electrodes which during operation of the furnace are submerged in the furnace charge. The electrodes are being held by electrode holders to which also electric operating current is being supplied to the electrodes. The electrodes are being regulated up and down in vertical direction by means of hydraulic cylinders in order to maintain a preset electrode current or a preset electric resistance. The electrode holder system further comprises means for slipping of the electrodes through the electrode holders to compensate for the electrode consumption.
The electrode tip positions in the furnace are important regulating parameters for operation of electric smelting furnaces. It has, however, been found that it is difficult to determine the electrode tip position at a sufficient accuracy. Conventionally, the electrode tip positions are measured by manual measurements which can only be done at long time intervals as manual determinations of electrode tip positions requires that the charge is melted down, whereafter the furnace has to be shut down in order to manually determine the electrode tip positions. This procedure causes interruption of the furnace operation and is therefore done as seldom as possible.
A number of other methods have been proposed for determination of the electrode length and the electrode tip position for electrodes in electric smelting furnaces. None of these methods have, however, found any use in practice. Electrode tip position as used herein shall mean the vertical position of the lower end of the electrode measured relative to a reference point on the smelting furnace. The reference point can for instance be the bottom of the smelting furnace. The electrode tip position will in this case be determined as the distance between the electrode tip and the furnace bottom.